1. Device Design: Stage 2 (Modified Microchannel Design)
Device Objective
To test the viability of a two-level passive micro-fluidic device
Modifications from Stage 1
Moved reservoir positions to fit existing packaging
Created discrete flow paths to test flow on individual layers and between layers
Increased all dimensions to facilitate fabrication and testing
Device Logic
Five distinct fluid paths
11 I/O
Two distinct channel
levels
One interconnect level
Insert the Correct Bryce Picture and have arrows indicate the four discrete fluid flow paths.
Explanation: What each path was meant to test.

2. Device Design: Stage 2 (Modified Microchannel Design)
Device Geometry
Chosen for process
compatibility
Rectangular micro-channels
Square Interconnects
Circular reservoirs
Materials
All PDMS layers on a Silicon substrate with SU8 for mold creation
Heightened design flexibility
PDMS biocompatibility
Equipment and material availability and fast turnaround time
Critical Dimension
Value
PDMS Layer Height
100mm
Micro-channel Width
500mm
Interconnect Width
1000mm
Interconnect Depth
Reservoir Diameter
0.4 cm
(Anne, Susan, Kunal)

3. Device Design: Stage 2 (Modified Microchannel Design)
Process Sequence and Mask Design
Begin with three polished Si wafers
Spin SU-8 (negative photoresist) on the Si wafers and pre-bake at 95°C
Align each of the three wafers with one of the three masks shown below and expose the SU-8 to ultraviolet light, then post-bake at 95°C
Develop the SU8 so that the unexposed areas are removed
Results in three distinct SU8 molds
Micro-Channel Layer 1 Interconnect Layer Micro-Channel Layer 2
(Anne, Susan, Kunal)

4. Device Design: Stage 2 (Modified Microchannel Design)
Spin PDMS on the SU8 molds less than the vertical dimension of the SU-8 protrusions
Mix PDMS (Sylgard 184, Dow-Corning) 10:1 with curing agent
Spin on PDMS
Dip the Si wafer in a sodium dodecyl sulfate(SDS) adhesion barrier and allow it to dry naturally
Bake in box furnace for 2 hours at 70°C
Delaminate and stack all three PDMS layers in the following order: Micro-channel Layer 1, Interconnect Layer, Micro-channel layer 2

5. Device Design: Stage 2 (Modified Microchannel Design)
Final Expected Result:
Insert the Correct Bryce Picture. Label, change angle, etc….

6. Device Design: Stage 3 (Pressure Actuated Valve Design)
Fluid Flow Modeling
Assumed Fluid Flow Rate based on Fluid velocity
Based on literature search: 1500 cm/minute= 2.5 E5 μm/sec
1.25 E 10 μm3/sec= cm3/sec
Fluidic Resistance: R= ΔP/Q [(N*s)/m5]
R(circular cross section)= 8μL/(πr4)
μ= Fluid Viscosity= 0.01 g/sec*cm
L= Length of channel
r= Radius of channel
R(Rectangular cross section)~ 12μL/(wh3)
w= Width of the channel
h= Height of the Channel
Total Fluidic Resistance = Rr + Rc + Ri + Rv
(Bryan, Kunal)
Rr Rc Ri Rv
RTotal

7. Device Design: Stage 3 (Pressure Actuated Valve Design)
Fluid Flow Modeling
Determined the velocity, fluidic resistance, Reynolds number and pressure gradient in each section of the fluids path and found the relevant total fluid path properties
Sample output for the two valve fluid path
Total Pressure Gradient
~15330Pa~115 Torr
Pressure Gradient at the Valve
3750 Pa~28 Torr
Fluid Flow Rate
1.25 E 10 μm3/sec= cm3/sec
Total Cycle Time
~21.2 seconds